manual settings circles was around a long time before computers, tables, cell phones where you can download software to tell you the exact coordinates at that time. what did they use to find the coordinates back then for the time they were viewing. donnie

I might still occasionally use them on a Super Polaris or Tak Space Boy - Polar aligned (very important), your DEC circle should be good to go. You then slew to a star with known coordinates, rotate the RA circle to match the star's RA (no harm making sure the DEC is correct as well, and a well-made mount will have the DEC scale properly aligned, and scope is parallel to polar axis), then you move the scope within the next couple of minutes (before the sky rotates too far away from your 'fixed' RA setting) to the RA and DEC coordinates that you wish to go to. That's it!

The only calculation one might make is to compensate for the 'epoch' of the published coordinates (due to earth's precession) - having a fancy HP-41 (or 67 for the even-more-ancient I suppose ) programmable calculator was the bee's knee!

manual settings circles was around a long time before computers, tables, cell phones where you can download software to tell you the exact coordinates at that time. what did they use to find the coordinates back then for the time they were viewing. donnie

We used these weird devices called "books" and "charts." Their displays were very low resolution, but they sure were easy on the batteries.

Seriously, knowing the exact epoch/coordinates was just not necessary given the low resolution of most amateur setting circles. Even in the 80s I could still use a 1950.0 atlas and manual setting circles and a great big Erfle to get objects.